1. Field of the Invention
This invention relates in general to certain new and useful improvements in a method for destroying microbial contamination, and more particularly, to a method of destroying microbial contamination in protein material by reducing the temperature of the protein material and thereafter applying gamma radiation in an amount sufficient to destroy any microbial contamination.
2. Brief Description of the Prior Art
In recent years, it has been recognized that tissues and fluids from human beings and other animals can be used quite effectively in research activities and in various diagnostic and theraputic activities. However, particularly for in-vivo use, it is necessary to insure that the protein material, such as the tissue or serum from a human being or other animal, is relatively free from microbial contamination, such as viral and bacterial and mycoplasma contamination.
It is well known that various disease forms can be readily and easily transmitted through blood transfusions. For example, it has been recognized that hepatitus and more recently, the acquired immune deficiency syndrome (AIDS) is transmitted through blood serum, as for example, during blood transfusions, or injections of purified protein, such as factor VIII.
Testing for hepatitis can be conducted by testing for the HB.sub.s AG antigen. However, for most diseases and abnormal conditions, the only effective means for screening doners of blood serum is that of a verbal inquiry. In many cases, the donor may deceive the interviewer about his or her medical condition in order to collect a monetary fee for the donated blood. However, more frequently, the donor may not even recognize the presence of any potential microbial contamination in the blood serum due to the fact that there may be a relatively long incubation period. Heretofore, and presently, there has been no effective means for readily determining the presence of at least viral contamination in a body serum.
It is important to obtain tissue culture which are viral and bacteria and mycoplasma free. It is also of importance to provide a tissue culture sera for use in testing activities and in research activities and which sera is also free of microbial contamination. Tissue culture sera are widely used to investigate contamination of implants such as breast implants, contact lenses, etc. Tissue culture and the sera for the tissue culture, which is a source of nutrient for the tissue culture, are often used for the growth of other protein material and often used to similulate an in-vivo situation. For example, tissue cultures and tissue culture sera are widely used in the production of vaccines. Thus, it is quite important that both the tissue culture and the tissue culture sera be free of any microbial contamination.
At present, it takes at very minimum, six weeks and oftentimes three months or longer to certify a fluid as free from such contamination. In order to determine whether or not there is any contamination, a cell regeneration is made and the viral activity is measured. Typically, techniques of this type, wherein cytopathological effect (CPE) is measured for viruses, are well known.
There have been attempts to measure the antigen level in a donors blood in order to determine whether or not viral activity was present. However, in many cases, it is virtually impossible to detect the virus by virtue of antigen level. This may be due to the fact that the virus may not have developed to a state where antigen is present. Thus, the viral contamination is incipient and may grow after such testing to a point where contamination is serious and thereby affect the recipient of any such tissue or serum.
It is possible to detect viral contamination by electron microscope measurements. However, these microscopes are very costly, require experience and known-how to operate and are generally not available at blood donor stations. Further, even if the microscopes could be provided, analysis would be time consuming and not effective due to the low concentration of virus is many infections. Thus, microscopic examination is an impractical method in most cases, and particularly in blood donations.
Heat treatment has been used for certifying albumin and other proteinaceous substances. In the case of albumin, the albumin is heated to at least 60 degrees C. for about ten hours. This has been found to be moderately effective for certifying albumin, although in many cases, it may not destroy all known bacterial and viral forms. In addition, this technique is not effective for many protein forms inasmuch as it may tend to significantly reduce the efficacy of the protein form.
Irradiation of blood components has been proposed, as for example, in "The Effects of Irradiation on Blood Components" by L. N. Button et al, presented in the American Association of Blood Banks annual meeting and accepted for publication May 18, 1980. This article describes cesium radiation with dosages varying from 500 to 8,000 rads and the article is only concerned with the destruction of lymphocytes in blood. This dosage is generally not believed to be sufficient to effectively destroy all contamination and further there is no suggestion of reducing temperature to protect the protein material.
It has been recognized that the method of certifying animal or human tissue or serum by anaylzing tissue or serum for presence of microbial contamination, is not truly effective. Therefore, more recent efforts have turned to some means or method for destroying the microbial contamination in the fluid thereby obviating the need for analysis. Further, there is a clear recognized need for some means or method for insuring certification of protein matter and particularly body serum, such as blood serums, by effectively destroying microbial contamination without substantially reducing the efficacy of the protein material.